How to remove log listeners for a pool:ed connections.

According to the documentation the setup callback is where you should do stuff like add log listeners to the connection. It works fine but when the connection is release back to the pool I get a warning that it still have a active log listener, which is correct but misleading.

• How/where should I remove the log listener?
• Is there a release callback somewhere that I have missed?
• I see that the warning is made using the warnings python api. I can just silence it but that might hide actual errors.

Example code:

pool = await asyncpg.create_pool(
    user='postgres',
    setup=lambda conn: conn.add_log_listener(_log_test),
)

After I have checked out a connection and released it back this gets printed to stdout/err:
/opt/python3.7/lib/python3.7/site-packages/asyncpg/connection.py:1295: InterfaceWarning: <wild.database.LeaderConnection object at 0x7f006d4e1208> is being released to the pool but has 1 active log listener

先从 connection-pool 文档以及 issue 中描述的 setup callback 行为开始。检查 asyncpg/connection.py 第 1295 行附近的代码，以理解 active-listener warning，并跟踪连接是如何释放的。当 listener 生命周期清晰，并且误导性的 warning 或缺失的释放机制已得到处理，同时没有隐藏无关的 warning 时，即可视为完成。